A129148 - OEIS

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A129148 as a simple table

n	a(n)
1	1
2	2
3	8
4	36
5	180
6	956
7	5300
8	30316
9	177604
10	1060284
11	6427092
12	39452364
13	244748196
14	1532044572
15	9664688436
16	61380865452
17	392148430212
18	2518518772604
19	16250624534420
20	105297028489612
21	684865176181348

[1,2,8,36,180,956,5300,30316,177604,1060284, 6427092,39452364,244748196,1532044572,9664688436, 61380865452,392148430212,2518518772604, 16250624534420,105297028489612,684865176181348]